Element to Boom attachment on a homebrew Yagi antenna?

[G6Tanuki]

I've got a big pile of 6mm aluminium alloy rods here, they were part of a lighting/display-panel setup. They're all exactly 1 Metre long, so my mind is drifting towards a 144MHz Yagi antenna, possibly a "Frankenyagi" using a mix of the attributes of the 1970s Viezbicke 'NBS Technical Note #688' designs and ideas culled from a RSGB manual of the mid-60s.

Problem is, how to attach the elements to the boom. The RSGB manual shows aluminium clips and a nut/bolt arrangement [see below] used with a circular boom but I intend to use a square-section boom because I've got a 2-Metre-long length of square 30mm alloy tube...

My thoughts are that I could use short lengths of modern UV-stable adhesive-lined heatshrink tube on the elements to keep them from sliding sideways through their holes in the boom. Maybe squirting some of the brown Gorilla Glue around the boom-to-element area before/after wielding the heat-gun?

It certainly seems a more-attractive and quicker approach than making up metal clamps.

My only worry is that adding what amounts to a dielectric over part of the elements might affect the resonant frequency... but who knows?

[pmmunro]

What about these?

https://www.springmasters.com/produc...filter_shaft=6

They are available in stainless steel but the data sheet doesn't appear to state what grade. The price seems reasonable as does the minimum order quantity.

Provided that the electrochemical potential between the clips and the boom material is not too great, there should not be a corrosion problem.

A call to the supplier might get the required information.

PMM

[G6Tanuki]

Now there's an attractive solution! May give them an email... Issues of position-in-the-electrochemical-series would be interesting though; I remember times-past where a supposedly-clued antenna manufacturer combined Brass and Aluminium in their connection-blocks... for use in a Marine environment!

The results, after a winter of storm-driven sea-spray, were a total mess.

[Jon_G4MDC]

Tig weld them. Low PIM solution.

I had to do have this done for a certain system that used 4stack dipoles around 200MHz.

[Radio Wrangler]

Too far away, but I've stuck plenty of aluminium antennae together and re-built the odd storm damaged sectional dish. It's easy enough where the rod is connected to the boom if you have the right gear and the right rods. Do you know anyone nearby with an AC TIG machine and pure Argon. It really needs to be an AC arc because the reverse direction current has a cleaning action and blows oxide platelets off.

David

[Steve G4WCS]

Interference fit hole so the element is fairly tight then a few pops around the periphery of the element with a spring loaded centre punch. Ill put up some pics of one Ive made when ive been in the garage. I probably dont need to tell you that the element length correction factor will be different mounting through the boom as opposed to on top of the boom

[Steve G4WCS]

Its a 23cm yagi with a 15mm round boom, may give you some ideas

[Steve G4WCS]

Ive also seen these plastic trim clips/rivets used, these will also isolate the element from the boom

[G6Tanuki]

Thanks all; Some interesting ideas there.... alas I don't have easy access to a TIG, and none of my vehicles have roofracks so transporting a 2.5 Metre long 1 Metre wide thing to someone who does have a TIG could be tricky.

Am going to try the starlock thing as my first attempt - waiting for a reply from the supplier mentioned upthread.

[BTW does anyone know what happened to Sandpiper Antennas in South Wales? THey used to be my go-to supplier for vsrious antenna bits and pieces but though the domain is still registered their website now forwards to a web-design company which makes me think they've either not renewed their hosting or have stopped tradingh]

[Dual Standard]

Aerial Parts of Colchester sell lots of antenna bits including pukka element clamps starting at at £1.10 (each).
http://aerial-parts.co.uk/epages/626...c/Products/800
They also sell complete antennas and some kits too.

Mike

[Aub]

Originally Posted by Steve G4WCS

Its a 23cm yagi with a 15mm round boom, may give you some ideas

Presumably the boom is electrically invisible to the reflector and director elements, at RF, as there is no physical insulation between them and the boom?

Cheers

Aub

[G6Tanuki]

Assuming the boom is a very-small-fraction of the wavelength of the driven-elements, the issue of the boom being connected/isolated from the elements can be disregarded.

[In times-past we built a crazy 10-element 28MHz Yagi using a bunch of 12-foot aluminium ladders as the 'boom' - we experimented with isolating the actual elements from the boom or directly-connecting them using car exhaust-pipe U-bolt clamps, and found no difference].

[Aub]

Thanks G6, I thought it must be along those lines.

Aub